This application claims the benefit of the Korean Application No. 2002-0029972 filed on May 29, 2002, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a color flat panel display, and more particularly, to an element for a color flat panel display which provides good image quality with a high contrast property by forming a reflecting layer on the display device, which is applied to the inner surface of a face plate, using a new metal material to remove halation caused by the reentry of scattered electrons from the rear surface of the fluorescent layer in the case of a display device using an electron beam.
2. Description of the Background Art
Generally, a cathode-ray tube (Brown tube) is mainly used as an image display device for color television. However, the cathode-ray tube has a very deep depth compared to the size of the front surface of the screen, caused by the structural characteristic of the cathode-ray tube. Therefore, it is impossible to fabricate a television picture receiver of the thin type.
Thus, apparatus using display devices such as an EL display element, a plasma display element, and a liquid crystal display element are developing as a flat panel display devices of the thin type. However, these devices have some problems, such as brightness, contrast, and color reproductibility when compared to the cathode-ray tube.
Japan Patent 3-184247 and Japan Patent 3-205751 disclose image display devices which construct a screen on a color television by dividing the picture on the screen into sections of a matrix and by deflecting irradiating electron beams toward respective sections to emit the fluorescent, with the object of displaying an image of high quality, similar to that of a cathode-ray tube, on a flat panel using an electron beam.
Hereinafter, an example of the conventional image display device described above will be described with reference to the accompanying Figures.
FIG. 1 is a view showing the structure of a conventional image display device.
As shown in FIG. 1, the image display device comprises: a glass container 1 defining a rear wall; a back electrode 2 of the plane plate type located at the front side of the glass container 1; a plurality of cathode filaments 3 of linear shape arranged at the front side of the back electrode 2 for discharging electrons; a control electrode 4, on which a plurality of penetrating holes are formed with a predetermined intervals therebetween, located at the front side of the cathode filaments 3; a plurality of signal modulation electrodes 5 arranged as bands and located at the front side of the control electrode 4 for controlling the electrons which passed through the penetrating holes in the control electrode 4; a focusing electrode 6 having a plane plate shape, and in which a plurality of slots are formed at predetermined intervals and located at the front side of the signal modulation electrode 5; a horizontal deflection electrode 7 formed by overlapping two plane plates of comb shape in the vertical direction and located at the front side of the focusing electrode 6; a vertical deflection electrode 8 formed by overlapping two plane plates of comb shape in horizontal direction and located at the front side of the horizontal deflection electrode 7; and a face plate 9 located at the front side of the vertical deflection electrode 8, including all components thereof, and maintaining the vacuum status therein by suitable coupling with the glass container 1.
The cathode filaments 3 are installed in the horizontal direction for generating electron beams distributed evenly in the horizontal direction, and a plurality of cathode filaments (4 filaments herein) are installed in the vertical direction while maintaining appropriate intervals therebetween. The cathode filaments 3 are made by applying an oxide cathode material on tungsten lines.
The back electrode 2 is made of a conductive material of plane plate shape, installed parallel with the cathode filaments 3.
The control electrode 4 is located at the front side of the cathode filaments 3 in the direction of the screen, faces the back electrode 2, and is made of a conductive plate in which rows of penetrating holes 4a, installed in a horizontal direction with appropriate intervals therebetween, are formed to be located on horizontal lines facing respective cathode filaments 3.
The signal modulation electrode 5 is made of a plurality of conductive plate rows which are thin and long in the vertical direction and arranged in positions facing the penetrating holes 4a of the control electrode 4, with predetermined intervals therebetween. The respective conductive plates include a plurality of penetrating holes 5a having the same shape as the penetrating holes 4a of the control electrode 4 at positions facing the penetrating holes 4a. 
The focusing electrode 6 includes penetrating holes 6a at positions facing the respective penetrating holes 5a of the signal modulation electrode 5.
The horizontal deflection electrode 7 consists of two conductive plates of comb shapes which are engaged with each other in the vertical direction with a predetermined interval on the same plane.
The vertical deflection electrode 8 consists of two conductive plates of comb shapes which are engaged with each other in a horizontal direction with a predetermined interval on a same plane.
The fluorescent layer emitting light by irradiation of an electron beam is applied to the inner surface of the face plate 9 to form a screen 20.
In addition, as shown in FIG. 3, the screen 20 is formed by applying a graphite layer 21 and a fluorescent layer 22 on an upper part of the face plate 9, and by applying an aluminum layer 23 on the upper parts of the graphite layer 21 and the fluorescent layer 22.
The control electrode 4, the signal modulation electrode 5, the focusing electrode 6, the horizontal deflection electrode 7, and the vertical deflection electrode 8 are attached by using insulating adhesives (not shown). The above components are arranged inside the image display device with constant intervals therebetween.
The operations of the above image display device will be described as follows.
Referring to FIG. 1, the cathode filaments 3 are heated by flowing electrical current in order to discharge the electrons easily. The electron beam of sheet-phase is discharged from the surface of the cathode filament 3 by applying appropriate voltages to the back electrode 2, to the cathode filaments 3, and to the control electrode 4 whereby the cathode filaments 3 are heated.
The electron beam of sheet-phase is divided into a plurality of bundles by the penetrating holes 4a of the control electrode 4 to form the plurality of electron beam bundles 11 (an electron beam bundle is represented in FIG. 1).
The amount of passage of the electron beam bundle 11 is controlled independently by the signal modulation electrode 5 corresponding to the image signal applied to the signal modulation electrode 5.
Next, the electron beam 5, which passes through the signal modulation electrode 5, is focused and shaped by the electrostatic lens effect of the penetrating holes 6a on the focusing electrode 6, and then deflected horizontally and vertically by the potential difference of the adjacent conductive plates of the horizontal deflection electrode 7 and the adjacent conductive plates of the vertical deflection electrode 8.
In addition, a high voltage, e.g., 10 kV, is applied to the graphite layer 21 of the screen 20, and therefore, the electron beam is accelerated with high energy and crashes with the graphite layer 21 to radiate the fluorescent layer formed on the inner surface of the face plate.
In more detail, when the television screen is divided as a matrix and the screen is set to be an aggregate of 10 divisions, the respective divided electron beam corresponds to respective 10 divisions. Therefore, the entire image to be presented is projected onto the screen 20 by causing the divided electron beam to correspond to respective 10 divisions to deflect and irradiate the electron beam only to the particular respective division.
Also, image signals of red, green, and blue colors corresponding to respective images are controlled by the signal modulation electrode 5 to reproduce the television moving pictures.
However, in the conventional image display device of the flat panel type, in the case where the electron beam is irradiated to both poles of the display device, some portion around the position where the electron beam is irradiated, glimmers, that is, generates the halation phenomenon.
The halation phenomenon is generated because the electron beam collides with the fluorescent layer of the screen 20 causing a portion of the electron beam to reenter into the fluorescent layer.
Especially, in the case where the voltages at both poles are high, the phenomenon can be prominently seen. Therefore, the contrast of the display device is reduced, a clear image cannot be obtained, and the functions of the display can become a big problem.
In order to solve the above problem, Japanese Patent Publications 5-314392, 6-231701, and 7-141998 have been suggested.
In Japanese Patent Publication 5-314932, the electron beam re-entry is restrained to be less than 30% by forming an aluminum layer on the fluorescent layer and controlling the thickness of the aluminum layer. In addition, it discloses that the thickness of the aluminum layer should be 2000 Å˜3500 Å in case that the voltage of aluminum layer on the face plate is 10 kV; 1500 Å˜3000 Å in the case where the voltage is 9 kV, and 1500 Å˜2000 Å in the case where the voltage is 8 kV.
In Japanese Patent Publication 6-231701, the fluorescent layer, the aluminum layer, and the carbon layer or boron containing layer are laminated on inner surface of a glass face, and fine embossing is formed on the surface of the aluminum layer facing the fluorescent layer. The carbon layer or the boron containing layer should be thicker than the aluminum layer; a gas discharge hole is formed in the carbon layer, and a gas discharge hole is formed as corresponding to the graphite in the black matrix.
Also, the carbon layer is made by laminating graphite particles having diameters of less than 1 μm to be a thickness of less than 1 μm. In addition, the boron layer instead of the carbon layer is formed by evaporating or sputtering.
In addition, the aluminum layer among the laminated layers is formed on the fluorescent layer using a transcription method which forms the layer on a predetermined film in advance.
In Japanese Patent Publication 7-141998, the ratio between the thickness and diameter of the carbon layer laminated on the aluminum layer is constructed to be 1:10 or more, and formed by laminating graphite granules having a sphere volume conversion average particle diameter of less than 2 μm.
In addition, the carbon layer is formed laminating the graphite granules in an amount of 20 μg/cm2˜220 μg/cm2 per unit area.
A representative embodiment of the above patents is shown in FIG. 3.
However, the above patents are not capable of effectively solving the halation problem.